Self-contained variable-environment pressing die



Nov. 10, 1964 SELF-CONTAINED VARIABLE-ENVIRONMENT PRES-SING DIE D. M. OLSON 3,156,011

Filed Jan. 10, 1962 ll 7 p 29 /9 INVENTOR. 24 3 Donald M. Olson United States Patent 3,156,011 SELF-CONTAINED VARIABLE-ENVIRONMENT PRESSTNG DIE Donald M. Olson, Los Alamos, N. Mex., assignor to the United States of America as represented by the United States Atomic Energy Commission Filed Jan. 10, 1962, Set. No. 165,464 2 Claims. (Cl. 13-16) This invention relates to a pressing die and more particularly to a novel self-contained variable-environment pressing die.

The pressing die of the present invention provides a versatile, portable unit capable of imposing a wide variety of preselected environmental conditions on a material specimen prior to, during and/ or after compaction. This unit eliminates the need for elaborate auxiliary equipment such as a dry box, transfer means, and heating equipment.

It is an object of the present invention to provide an improved apparatus which makes possible experimental pressing of powders in a selected gaseous environment at any gas pressure from 10- mm. Hg to 100 p.s.i.g. simultaneously with temperatures from ambient to 1000 F,

without requiring cumbersome dry box handling, in which the selected environment can be maintained prior to, during and/ or after pressing operations.

It is another object of the present invention to provide an improved apparatus in which simple punch and die changes make possible a wide range of specimen diameters and pressing pressures.

It is a further object to provide an improved die assembly which is easily converted from a single to a double acting punch.

It is a still further object of the invention to provide an improved die assembly unit which is compact and portable, and in which the auxiliary heating, vacuum pumping, and power equipment are simple and portable. The only power supply required is ordinary 110 volt house current. The unit can be used in any press having a 12- inch clearance between the platens. A commercial hydraulic truck jack can be used for the press.

The improved die assembly will be used as an experimental tool in powder metallurgy programs, examples of which are as follows:

(1) A study of the effect of in die reduction of metal powder on properties of the cold pressed product. The die containing a metal powder specimen would be evacuated, H gas introduced to some selected pressure, and the specimen heated at temperatures of about 500 C. to remove surface oxide. This clean up reduction could be carried out either in a static or flowing H atmosphere. The pressing operation can then be carried out with the powder in H atmosphere at some preselected pressure, or the die can be evacuated and pressing carried out in vacuum.

(2) A study of the eifect of reduced environmental pressure, per se, on the properties of as-pressed powders.

(3) A study of the effect of various gaseous environments on properties of pressed powders. Interesting changes in compactability of various powders may be brought about by varying the gaseous environment.

(4) A study of the effect of in die H reduction at low temperature and immediate subsequent compaction on sinterability of coprecipitated-coreduced complex metal oxides.

(5) A study of the effect of low temperature (ambient to 1000 F.) pressing on the properties of compacted refractory metals (W, Mo).

These and various other objects, features and advantages of the invention will be better understood from the following description taken in connection with the accompanying drawing, in which The figure is a vertical, partial cross-sectional view of a self-contained variable-environment pressing die which embodies the present invention.

In the figure the die assembly consists of an interchangeable, hollow, cylindrical die 1 surrounded by a high strength die container 2 which also serves as the basic environmental enclosure. A split die can be used to facilitate removal of fribble or weak compacts pressed at low pressures. The die is shown for use as a single action punch. When used as such, the die container 2 is enclosed and sealed at the bottom with a simple compression block 3 by means of quick acting clamp 5 and 0-ring 6. A back-up punch 4 is seated in the die cavity against the compression block.

A metal betllows 7 encloses the guide and punch assembly at the top of the die container. This assembly consists of guide 8 which is sealed to the die container 2 by means of quick acting clamp 9 and O-ring 10. Fitted within guide 8 is a bearing 11 Within which the punch 12 is slidably positioned. The bellows 7 is sealed to guide 8 by means of clamp 13 and O-ring 14. The punch 12 is attached at the top to holder 15 by means of dog 16. The bellows 7 is sealed to holder 15 by means of clamp 17 and O-ring 18. The bellows 7 is soldered at both ends to clamps 1'7 and 13. A spring 19 holds the punch 12 in its upward preactuation position.

A lower guide, punch and bellows assembly can be easily interchanged with the compression and backup punch assembly to convert the die to a double action punch. The dies and punches are interchangeable units making possible the selection of die and punch materials best suited to use and environment, and providing wide latitude in specimen diameter, geometry, and pressing pressures.

For work at room temperature or slightly elevated temperatures (up to 200 C.), commercial rubber or Teflon O-rings are used. At higher temperatures (above 200 C.), metal O-rings are used.

The die is designed so that the die cavity can be evacuated, and pressing carried out at pressures as low as 10* mm. Hg, or after evacuation, a preselected gas or gas mixture can be admitted to the die cavity at some preselected pressure from 10 mm. Hg to p.s.i.g. The insert die can be heated to 1000 F., and this temperature maintained during treatment prior to pressing and/ or during the actual pressing operation.

The die is evacuated by means of a vacuum pump 29 connected to the environmental control valve 20. Valve 20 is attached to guide 8 by means of tube 22 which is in communication with passageway 23 through the guide to the die cavity. Pressure gage 21 is attached for convenience to tube 22. Valve 20 may be provided with throttling control at the start of pump down to prevent the powder specimen from being sucked out the vacuum line. Valve 20 is used also for the admission of the de sired gaseous environment. The environmental gases may be taken from a pressurized tank supply 30 through, if required, a suitable purification and drying train. Valve 20 may be a simple two-way valve for connection to either the vacuum pump or the bottle supply. Pressure measurements in the vacuum range may be measured by means of an ion gage.

Any type of press equipment is suitable for use, from an ordinary hand operated hydraulic press to more elaborate testing equipment, depending on experimental requirements. For example, a 60,000 machine has been used. The die is designed to withstand the full machine load, or a working pressure of 300,000 p.s.i. on a 0.5-inch diameter punch face.

The insert die 1 can be heated to 1000 F. and this temperature maintained prior to and/or during pressing by means of a heating element 31 in the die. Passage 24 in the compression block is provided for the electrical connections from the heating elements in the die to the power source. Die heating may be accomplished by nichrome resistance elements encapsulated in Alundum and inserted into cavity 25 in the die 1. In an experimental check of heating, it was found that four such heaters operated in series at 30 volts gave an equilibrium temperature at the die wall of 465 C. in approximately 45 minutes. Heaters can be readily replaced in case of burnout. Power to the heaters may be supplied by a 120-volt, 60-cycle line through a variac.

Burn-oil. tube 26 is attached to opening 27 in guide 8. Tube 26 may serve as either an entry into the die cavity for fine wire thermocouples or as a burn-off flare for operations involving flowing H A glass-to-metal seal is used on tube 26 when the die is used for vacuum operations.

In operation, the desired quantity of powder may be introduced into the die cavity 28 after removing guide 8 from its position shown in the figure. After the powder has been introduced into the die cavity 28 the unit may be assembled. By proper manipulation of valve 20 the desired environmental conditions within the die cavity may be achieved. By adjusting the variac (not shown) included in the power supply, which variac may be calibrated in terms of temperature, the desired temperature within the die may be achieved. After the desired pressure has been applied the unit may be disassembled and the powder compact removed.

As other modifications and variations of the present invention will be obvious to those skilled in the art, the invention is not intended to be restricted to the specific embodiment described but to be construed broadly within the spirit and scope of the invention as set forth in the following claims.

What is claimed is:

1. A self-contained variable-environment pressing die comprising a cylindrical die having a die cavity and a hollow portion annular to said die cavity within the wall, a cylindrical die container surrounding said die, a compression block sealed to and enclosing the bottom of said die container, a backup punch sealed in the bottom of said die cavity and positioned against said compression block, a guide block sealed to and enclosing the top of said die container and provided with a cylindrical guide aperture in alignment with said die cavity, a punch slidably positioned within said cylindrical aperture, a punch holder connected to said punch at its end most remote from said die cavity, a metal bellows sealed between said guide block and said holder, a spring positioned within said bellows and extending between said guide block and said holder whereby the punch is held in its upward preactuation position, resistance heating means Positioned within the hollow portion of the Wall of said die, electrical connection means connected to said heating means and extending through said compression block for connecting said heating means to an external voltage source, a conduit in communication with the die cavity extending externally of said assembly, a valve connected to said conduit, a pressurized gas container connected to said valve, and means for controlling the gaseous environment during pressing operations such that a selected gas is present in the die cavity during the pressing operation at any selected pressure between subatrnospheric and superatmospheric.

2. A pressing die as set forth in claim 1 wherein the valve is a control valve capable of throttling at the start of pumpdown so that the powder will not be sucked out of the vacuum line.

References Cited in the file of this patent UNITED STATES PATENTS 1,071,488 Weintraub et a1. Aug. 26, 1913 1,918,064 Taylor July 11, 1933 2,169,281 Pfanstiehl Aug. 15, 1939 2,195,297 Engle Mar. 26, 1940 2,437,127 Richardson Mar. 2, 1948 2,457,756 Vest Dec. 28, 1948 2,518,137 Gorecki Aug. 8, 1950 2,651,700 Gans Sept. 8, 1953 2,694,922 Vilella Nov. 23, 1954 2,882,143 Schmidt et a1 Apr. 14, 1959 FOREIGN PATENTS 535,576 Canada Jan. 8, 1957 

1. A SELF-CONTAINED VARIABLE-ENVIRONMENT PRESSING DIE COMPRISING A CYLINDRICAL DIE HAVING A DIE CAVITY AND A HOLLOW PORTION ANNULAR TO SAID DIE CAVITY WITHIN THE WALL, A CYLINDRICAL DIE CONTAINER SURROUNDING SAID DIE, A COMPRESSION BLOCK SEALED TO AND ENCLOSING THE BOTTOM OF SAID DIE CONTAINER, A BACKUP PUNCH SEALED IN THE BOTTOM OF SAID DIE CAVITY AND POSITIONED AGAINST SAID COMPRESSION BLOCK, A GUIDE BLOCK SEALED TO AND ENCLOSING THE TOP OF SAID DIE CONTAINER AND PROVIDED WITH A CYLINDRICAL GUIDE APERTURE IN ALIGNMENT WITH SAID DIE CAVITY, A PUNCH SLIDABLY POSITIONED WITHIN SAID CYLINDRICAL APERTURE, A PUNCH HOLDER CONNECTED TO SAID PUNCH AT ITS END MOST REMOTE FROM SAID DIE CAVITY, A METAL BELLOWS SEALED BETWEEN SAID GUIDE BLOCK AND SAID HOLDER, A SPRING POSITIONED WITHIN SAID BELLOWS AND EXTENDING BETWEEN SAID GUIDE BLOCK AND SAID HOLDER WHEREBY THE PUNCH IS HELD IN ITS UPWARD PREACTUATION POSITION, RESISTANCE HEATING MEANS POSITIONED WITHIN THE HOLLOW PORTION OF THE WALL OF SAID DIE, ELECTRICAL CONNECTION MEANS CONNECTED TO SAID HEATING MEANS AND EXTENDING THROUGH SAID COMPRESSION BLOCK FOR CONNECTING SAID HEATING MEANS TO AN EXTERNAL VOLTAGE SOURCE, A CONDUIT IN COMMUNICATION WITH THE DIE CAVITY EXTENDING EXTERNALLY OF SAID ASSEMBLY, VALVE CONNECTED TO SAID CONDUIT, A PRESSURIZED GAS CONTAINER CONNECTED TO SAID VALVE, AND MEANS FOR CONTROLLING THE GASEOUS ENVIRONMENT DURING PRESSING OPERATIONS SUCH THAT A SELECTED GAS IS PRESENT IN THE DIE CAVITY DURING THE PRESSING OPERATION AT ANY SELECTED PRESSURE BETWEEN SUBATMOSPHERIC AND SUPERATMOSPHERIC. 